Architecture for multi-domain natural language processing

ABSTRACT

Features are disclosed for processing a user utterance with respect to multiple subject matters or domains, and for selecting a likely result from a particular domain with which to respond to the utterance or otherwise take action. A user utterance may be transcribed by an automatic speech recognition (“ASR”) module, and the results may be provided to a multi-domain natural language understanding (“NLU”) engine. The multi-domain NLU engine may process the transcription(s) in multiple individual domains rather than in a single domain. In some cases, the transcription(s) may be processed in multiple individual domains in parallel or substantially simultaneously. In addition, hints may be generated based on previous user interactions and other data. The ASR module, multi-domain NLU engine, and other components of a spoken language processing system may use the hints to more efficiently process input or more accurately generate output.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/720,909, filed Dec. 19, 2012, now U.S. Pat. No. 9,070,366, which isincorporated by reference herein in its entirety.

BACKGROUND

Spoken language processing systems include various modules andcomponents for receiving speech input from a user, determining what theuser said, and determining what the user meant. In some implementations,a spoken language processing system includes an automatic speechrecognition (“ASR”) module that receives audio input of a user utteranceand generates one or more likely transcriptions of the utterance. Spokenlanguage processing systems may also include a natural languageunderstanding (“NLU”) module that receives textual input, such as atranscription of a user utterance, and determines the meaning of thetext in a way that can be acted upon, such as by a computer application.For example, a user of a mobile phone may speak a spoken command toinitiate a phone call. Audio of the spoken command can be transcribed bythe ASR module, and the NLU module can determine the user's intent(e.g., that the user wants to initiate the phone call feature) from thetranscription and generate a command to initiate the phone call.

Text-to-speech (“TTS”) systems convert text into sound using a processsometimes known as speech synthesis. In a common implementation, a TTSsystem may receive text input and provide an audio presentation of thetext input to a user. For example, a TTS system may be configured to“read” text to a user, such as the text of an email or a list ofreminders.

Some systems combine both speech recognition and TTS. For example,global positioning systems (“GPS”) can receive a user's spoken inputregarding a particular address, generate directions for travelling tothe address, and aurally present the directions to the user. In manycases, users may then continue to interact with such systems whilereceiving directions. After the GPS system provides the next directionor series of directions, the user may use one of any number ofpredetermined commands (e.g., “cancel route,” “next turn”). In addition,other non-spoken user interactions may be used to interact with contentthat is presented aurally. For example, turn-by-turn directions can bedisplayed via a touch screen display that allows users to select, via atouch screen or keyboard, a particular route to bypass.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of various inventive features will now be described withreference to the following drawings. Throughout the drawings, referencenumbers may be re-used to indicate correspondence between referencedelements. The drawings are provided to illustrate example embodimentsdescribed herein and are not intended to limit the scope of thedisclosure.

FIG. 1 is a block diagram of an illustrative networked environment inwhich a spoken language processing system may be implemented, showingillustrative interactions between a spoken language processing system, aclient device, and a user.

FIG. 2 is a block diagram of an illustrative spoken language processingsystem showing data flows between various modules.

FIG. 3 is a block diagram of an illustrative multi-domain naturallanguage understanding module.

FIG. 4 is a flow diagram of an illustrative process for saving history,generating hints, and using the history and hints to process userinteractions.

FIG. 5 is a flow diagram of an illustrative process for processing anutterance that may apply to one of multiple domains.

DETAILED DESCRIPTION

Spoken language processing systems can perform more efficiently andaccurately when they know the subject matter to which the spokeninteractions that they process relate. For example, an automatic speechrecognition (“ASR”) module of a spoken language processing system mayutilize various models (e.g., language models, acoustic models) whendetermining the content of a spoken user interaction, also known as anutterance. The ASR module may utilize specialized models for aparticular subject matter, also known as a domain, when the ASR moduleknows the domain to which the utterance relates. Such specialized modelscan improve the efficiency and accuracy of the ASR module. Other modulesof a spoken language processing system, such as a natural languageunderstanding (“NLU”) module, may interpret the user's words (e.g., asreceived from an ASR module) to determine what action the user wouldlike to initiate, also known as a user intent. An NLU module may beconfigured to interpret the user's words into an action within aparticular domain. If the user's words do not support an interpretationwithin the particular domain for which the NLU module is configured, theNLU processing may be inefficient and error-prone, or the NLU module maynot be able to generate any reasonable interpretation.

Some spoken language processing systems are configured to processutterances within one of any number of different domains. Such systemschoose one domain in which to process an utterance. For example, asystem may expect a user utterance to relate to a currently activedomain and therefore only process the utterance with respect to thatparticular domain. A user may initially wish to get directions, and mayinitiate a series of interactions (e.g., utterances and responses) withthe spoken language processing system in order to get directions. Atsome point while the user is getting directions, the user may decide toperform a different task instead, such as initiating playback of music.The user may issue a spoken command to initiate playback of music.However, the spoken language processing system, expecting an utterancein the “directions” domain, may not understand or may misinterpret thespoken command. In some cases, the spoken language processing system maynot understand the spoken command even if the spoken command is formedproperly such that it would be understood by the spoken languageprocessing system if it was processed in the music domain.

Aspects of this disclosure relate to processing user utterances inmultiple domains and, based on the results, selecting the most likely orappropriate domain in which to generate a response or otherwise takefurther action. A user utterance may be processed by an ASR module. Atranscription or N-best list of transcriptions from the ASR module maybe provided to a multi-domain NLU engine. The multi-domain NLU enginemay use any number of individual domain-specific NLU modules to processthe transcription in multiple domains at the same time or substantiallythe same time (e.g., in parallel or asynchronously). After thedomain-specific NLU modules have produced results (e.g., determined oneor more likely interpretations) and, optionally, scores for thoseresults (such as a confidence score or a likelihood score), the mostlikely or appropriate interpretation may be selected. In this way, aspoken language processing system may be more responsive to userutterances and allow users to arbitrarily switch domains without firstinforming the spoken language processing system of the domain to whichthe user is switching for a particular utterance.

Additional aspects of the disclosure relate to analyzing previous userinteractions and generating processing hints, also referred to hereinsimply as hints, to aid in processing of user utterances. Each userinteraction with a user device or a spoken language processing systemmay create history, or context, that can be used to determine the user'sintent when processing a subsequent utterance. In addition, specifichints may be generated regarding what the user is likely to do next. Forexample, a user may engage in a series of directions-related andmusic-related activities (e.g., getting driving directions to variouslocations and playing music from various artists). History regardingthese activities may be saved and then considered by the various modulesof the spoken language processing system. Subsequent interactions may bemore likely to relate to the same or similar domains as the previousinteractions. In addition, recent interactions may be used to generatehints regarding what the user would like to do next. For example, if aspoken language processing system prompts a user for the artist or titleof a requested song, there is a substantial likelihood that the nextuser utterance will relate to an artist or a song title. However, asmentioned above, the utterance may be processed in multiple domains sothat if the user does decide to do something different or otherwise doesnot provide an artist or song title, the spoken language processingsystem may still process the utterance accurately and respondappropriately.

Although aspects of the embodiments described in the disclosure willfocus, for the purpose of illustration, on a spoken language processingsystem exchanging data with a separate client device via a network, oneskilled in the art will appreciate that the techniques disclosed hereinmay be applied to any number of software processes or applications. Forexample, a client device may include a speech recognition engine andprovide the features described herein for processing user utterances inmultiple domains to determine the most appropriate domain for any givenutterance. Various aspects of the disclosure will now be described withregard to certain examples and embodiments, which are intended toillustrate but not limit the disclosure.

With reference to an illustrative example, a user may issue spokencommands or otherwise make spoken utterances to a client device, such asa mobile phone or tablet computer. The utterances may be transmitted toa network-accessible speech recognition server, which processes theutterances and returns a response. FIG. 1 illustrates such a spokenlanguage processing system 100 in communication with a client device102.

The spoken language processing system 100 may use an ASR module toprocess the utterance and transcribe what the user said. In addition,history data may be saved regarding the utterance. The history data mayinclude a copy of the transcription or N-best transcriptions, or summarydata regarding the transcription. The history data may also include atimestamp so that the spoken language processing system 100 maydetermine which history data is the most recent, etc.

The spoken language processing system 100 may use a multi-domain NLUengine to determine what the user would like to do, also known as theuser intent, based on the transcription from the ASR module. Themulti-domain NLU engine may also consider hints or history based onprevious user interactions or other data when determining the userintent. The multi-domain NLU engine can include any number ofdomain-specific NLU modules configured to operate on text related to aparticular subject matter or in a particular domain (e.g., gettingdirections, shopping, initiating communication with a contact,performing a search, or playing music). Domain-specific NLU modules mayprocess text, such as a transcription, with respect to a particulardomain and produce a result indicating the user's intent. Suchdomain-specific NLU modules are known in the art and will not bedescribed in detail here.

Advantageously, in a multi-domain NLU engine, each of thedomain-specific NLU modules can process the transcription in parallel,with each module producing a separate result indicating the user'sintent (e.g., the user wants directions, or the user wants to listen tomusic). The multi-domain NLU engine or some other module or component ofthe spoken language processing system 100 can then select a particulardomain-specific result on which the spoken language processing system100 will base its response. The selection may be based on a likelihoodthat each individual result is reflective of the user's actual intent.

As illustrated in FIG. 1, the spoken language processing system 100 mayreceive and respond to several utterances related to the “directions”domain at (A). For each of the utterances, however, the domain-specificNLU modules for other domains also process the utterance in parallelwith the directions domain-specific NLU module. The results returnedfrom the other domain-specific NLU modules may be less likely to reflectthe user's actual intent, however, due to the language used by the userand the language that is typically used when a user intends to interactwith the individual domains. As a result, the spoken language processingsystem 100 may decide to produce a response to the utterance based onthe result returned by the directions domain-specific NLU module.

In some cases, the response generated by the spoken language processingsystem 100 may be a clarifying question (e.g., if the user utterance wasambiguous), requested information (e.g., if the user utterance requesteddriving directions), a command for execution by the client device (e.g.,if the user utterance was a spoken command to initiate voice dialing ofa phone), etc. For example, the spoken language processing system 100may use a text-to-speech (“TTS”) module to generate synthesized speechthat the user may consume or with which the user may interact. If theuser has submitted spoken commands requesting driving directions, thespoken language processing system 100 may use the TTS module to generateaudio of the driving directions. The spoken language processing system100 may transmit the TTS audio to the client device 102 at (B). Theclient device 102 may receive the TTS audio and play it to the user at(C). As seen in FIG. 1, the TTS audio may include directions that theuser requested.

After any number of utterances related to the directions domain, theuser may issue a spoken command that is related to a different domain at(D). Illustratively, the user utterance may be “Play Beethoven's 5thSymphony.” Such an utterance is a command to initiate playback of aparticular musical recording. The client device 102 may transmit dataregarding the user's utterance to the spoken language processing system100 at (E).

After generating a transcript for the utterance through the use of theASR module, the spoken language processing system 100 can process theutterance in a multi-domain NLU engine at (F). In the present example,the NLU module for the music domain may produce several potentialinterpretations, including one indicating that the user intends to heara recording of Beethoven's 5th Symphony, while the NLU module for thedirections domain may return several potential interpretations,including one indicating that the user intends to get directions to arestaurant named Beethoven's that is located on 5th Street. There may beany number of other domain-specific NLU modules that return results, andthe results may be more or less plausible depending on the particulardomain.

In addition to the results, the domain-specific NLU modules may, in someembodiments, return scores regarding the likelihood that each resultcorresponds to the user's actual intent. In the current example, theresult from the music domain may have a high score because Beethoven's5th Symphony is an actual music recording. In addition, if the user hasaccess to a musical recording of Beethoven's 5th Symphony, the score maybe further increased. Moreover, if the user's recent history includesother requests to hear music recordings of Beethoven's music or those ofanother classical composer, the score may be increased further. Theresult from the directions domain may also have a relatively high score,due to the recent history of directions-related interactions. The scoremay be relatively high particularly if there is a restaurant namedBeethoven's and the restaurant is on 5th Street. However, due to thelack of a completely applicable result (e.g., the terms “play” and“symphony” do not relate to directions), the score may be low enoughthat the music domain interpretation's score is higher and therefore isthe one on which the spoken language processing system 100 bases itsresponse.

After automatically selecting the interpretation from the music domainat (G), the spoken language processing system 100 can prepare a responseat (H). In the current example, the response may be an executablecommand that the client device 102 executes. The executable command mayindicate the task to perform (e.g., play music), and parameters or otherdata relevant to the task (e.g., a song ID or the artist and songtitle). The spoken language processing system 100 can transmit theresponse to the client device 102 at (I). The client device 102 canexecute the response at (J), playing the requested musical performanceto the user. In some embodiments, the spoken language processing system100 can prepare other responses, such as streaming the selected song,causing another system to stream the selected song, etc. In practice,the response executed by or transmitted from the spoken languageprocessing system 100 can vary depending on the domain and thecapabilities of the client device 102, among other factors.

Distributed Spoken Language Processing System Environment

Prior to describing embodiments of processes for analyzing userutterances in a multi-domain NLU engine in detail, several illustrativeinteractions and an example environment in which the processes may beimplemented will be described. FIG. 2 illustrates a spoken languageprocessing system 100 and a client device 102. The spoken languageprocessing system 100 can be a network-accessible system incommunication with the client device 102 via a communication network150, such as a cellular telephone network or the Internet. A user mayuse the client device 102 to submit utterances, receive information, andinitiate various processes, either on the client device 102 or at thespoken language processing system 100. For example, the user can issuespoken commands to the client device 102 in order to get directions orlisten to music, as described above.

The client device 102 can correspond to a wide variety of electronicdevices. In some embodiments, the client device 102 may be a mobiledevice that includes one or more processors and a memory which maycontain software applications executed by the processors. The clientdevice 102 may include a speaker or other audio output component forpresenting or facilitating presentation of audio content. In addition,the client device 102 may contain a microphone or other audio inputcomponent for accepting speech input on which to perform speechrecognition. Illustratively, the client device 102 may be a mobilephone, personal digital assistant (“PDA”), mobile gaming device, mediaplayer, electronic book reader, tablet computer, laptop computer, andthe like. The software of the client device 102 may include componentsfor establishing communications over wireless communication networks ordirectly with other computing devices.

The spoken language processing system 100 can be any computing systemthat is configured to communicate via a communication network. Forexample, the spoken language processing system 100 may include anynumber of server computing devices, desktop computing devices, mainframecomputers, and the like. In some embodiments, the spoken languageprocessing system 100 can include several devices physically orlogically grouped together, such as an application server computingdevice configured to perform speech recognition on an utterance and adatabase server computing device configured to store records and speechrecognition models.

The spoken language processing system 100 can include an orchestratormodule 110, an ASR module 112, a multi-domain NLU engine 114, a dialogmanager 116, a natural language generation (“NLG”) module 118, and a TTSmodule 120. In some embodiments, the spoken language processing system100 can include various modules and components combined on a singledevice, multiple instances of a single module or component, etc. Forexample, the spoken language processing system 100 may include aseparate orchestrator 110 server that may be configured with a dialogmanager module 116; a server or group of servers configured with ASR andNLU modules 112, 114; and a server or group of servers configured withNLG and TTS modules 118, 120. In multi-device implementations, thevarious devices of the spoken language processing system 100 maycommunicate via an internal communication network, such as a corporateor university network configured as a local area network (“LAN”) or awide area network (“WAN”). In some cases, the devices of the spokenlanguage processing system 100 may communicate over an external network,such as the Internet, or a combination of internal and externalnetworks.

In some embodiments, the features and services provided by the spokenlanguage processing system 100 may be implemented as web servicesconsumable via a communication network 150. In further embodiments, thespoken language processing system 100 is provided by one more virtualmachines implemented in a hosted computing environment. The hostedcomputing environment may include one or more rapidly provisioned andreleased computing resources, which computing resources may includecomputing, networking and/or storage devices. A hosted computingenvironment may also be referred to as a cloud computing environment.

The network 150 may be a publicly accessible network of linked networks,possibly operated by various distinct parties, such as the Internet. Inother embodiments, the network 150 may include a private network,personal area network (“PAN”), LAN, WAN, cable network, satellitenetwork, etc. or some combination thereof, each with access to and/orfrom the Internet. For example, the devices of the spoken languageprocessing system 100 may be located within a single data center, andmay communicate via a private network as described above. The clientdevice 102 may communicate with spoken language processing system 100via the Internet. The client device 102 may have access to the Internetvia a wired or WiFi connection, or via a cellular telephone network(e.g., a Long Term Evolution or LTE network).

In operation, the client device 102 may transmit audio and other data tothe spoken language processing system 100, and receive audio, executablecommands, and other data from the spoken language processing system 100in response. The orchestrator 110 may oversee receipt of input from theclient device 102 and routing of the data within the spoken languageprocessing system 100 in order to process the input and generate aresponse.

For example, the input from the client device 102 may be a userutterance transmitted to the spoken language processing system 100 viathe network 150. The orchestrator 110 may route the utterance to the ASRmodule 112 to be processed into a transcription or a lattice or N-bestlist of transcriptions. Hints can be provided to the ASR module 112 toaid in processing. Illustratively, a hint may be used to inform the ASRmodule 112 that the utterance is likely to include a title to a song bya particular artist because the user was just prompted for a song titleafter requesting to hear music by the artists. The ASR module 112 mayuse the hint to narrow its search space regarding which words may beincluded in the utterance, potentially providing an improvement inefficiency and accuracy.

The transcription or N-best list of transcriptions generated by the ASRmodule 112 can be provided to the multi-domain NLU engine 114 todetermine the specifics of the request and to formulate a command tosatisfy the request. In addition, the dialog manager 116 or some othercomponent of the spoken language processing system 100 may generate ahint for the multi-domain NLU engine 114, such as data indicating thelikelihood that the transcription relates to a song title of theparticular artist due to the previous TTS prompt to the user for a songtitle to play. By hinting this likelihood to the multi-domain NLU engine114, NLU processing may determine the user's intent more efficiently andaccurately, and scores, if used, may be weighted accordingly. Ifadditional information is required (e.g., the utterance was ambiguous ordid not include all necessary information), the orchestrator 110 mayprovide data to the dialog manager 116 regarding the most likely userintents. The dialog manager 116 can then formulate a response to theuser that prompts the user for the appropriate information. The responsemay be generated in the form of semantic frames (or some other semanticrepresentation of text) which indicate the information that is requiredor desirable. Another component, such as the NLG module 118, cangenerate text for the question to be asked of the user.

When text or synthesized speech is to be transmitted to the clientdevice 102, information about the desired output may be provided to anNLG module 118 in the form of semantic frames to generate naturallanguage text for the responses and prompts. In some embodiments, hintsmay also be provided to aid in NLG processing. The NLG module 118 cananalyze the semantic frame (e.g., prompt the user for more informationabout getting directions to a specific location). The NLG module 118 canthen generate textual content (including TTS markup regarding the wordson which to put spoken emphasis, and other such features of spokenlanguage) that sounds natural when read or synthesized into speech bythe TTS module 120.

The orchestrator 110 may employ the TTS module 120 to generate an audiopresentation of text content and TTS markup, whether the text is a userprompt, information requested by the user, or some other text. Theorchestrator 110 may then transmit the audio generated by the TTS module120 to the client device 102. In addition, the orchestrator 110 or someother component of the spoken language processing system 100 may savehistory regarding the fully processed interaction, generate hints forsubsequent interactions, and the like.

FIG. 3 illustrates a detailed example of a multi-domain NLU engine 114.The multi-domain NLU engine 114 can receive transcriptions of userutterances, textual input from users (e.g., input that users have typedon a client device 102 and submitted) or other textual input. Themulti-domain NLU engine 114 can output interpretations of the textualinput that may be acted upon by other components of the spoken languageprocessing system 100. The interpretations may include a user intent(e.g., “play a song”) and one or more named entities that addinformation to be used in acting upon the user intent (e.g., a “song”entity with a value “Gimme Shelter” and an “artist” entity with a value“Rolling Stones”).

A multi-domain NLU engine 114 may include any number of single-domainNLU modules 202. For example, the multi-domain NLU engine 114 mayinclude a music domain 202 a, a directions domain 202 b, and a phonedialing domain 202 c. A cross-domain ranker 204 may receive the resultsprovided by various single-domain NLU modules 202 (e.g., the N-best listfrom each single domain NLU module 202) and compile them into a combinedresult (e.g., one N-best list including the results from allsingle-domain NLU modules 202). The slot filler 206 can correcterroneous data in the results (e.g., correct song titles by checkingagainst a catalog of known song titles). In addition, the slot filler206 can filter data that is included in the results so that onlyinformation useful to other components of the spoken language processingsystem 100 is included. The context ranker 208 can determine whichresult is the most appropriate. The context ranker 208 may analyzescores to choose a single domain or result with which to proceed, or thecontext ranker 208 may generate an N-best list of likely user intentsacross all domains.

Each single-domain NLU module 202 may include several modules thatimplement various portions of NLU domain processing. As seen in FIG. 3,a single-domain NLU module 202 can include a tokenizer 220, a namedentity recognizer 222, and an intent classifier 224. Some embodimentsmay include fewer or additional modules rather than only those shown inFIG. 3.

In operation, the multi-domain NLU engine 114 can receive atranscription or N-best list of transcriptions, such as those generatedby an ASR module 112. The multi-domain NLU engine 114 can also receivehints, such as those generated by the dialog manager 116. Themulti-domain NLU engine 114 may then initiate processing of thetranscription in each available single-domain NLU module 202. Theprocessing in the individual domains may proceed in parallel, such thatprocessing of a transcription in multiple domains may take substantiallythe same amount of time as processing in a single domain.

The tokenizer 220 can transform a transcription from a collection ofwords into a series of tokens that may be processed. The tokenizer 220may use various lexica to normalize words. For example, the tokenizer220 can remove punctuations, convert digits to words (e.g., “911” to“nine one one”), etc.

The named entity recognizer 222 can label or tag individual words ortokens for further processing. For example, in the utterance “I want toplay Gimme Shelter by the Rolling Stones,” the words “I,” “want,” and“to” may be labeled as “other” because they do not, by themselves,indicate any specific user intent or provide any meaningful information.The next word, “play,” indicates the command that is to be performed.Such a word or token may be labeled as a user intent, because the userintends for the system to play a song. The phrase “Gimme Shelter” may belabeled as a song title, while the phrase “Rolling Stones” may belabeled as an artist. Finally, the words “by the” may be labeled“other,” because they are not actionable and provide no additionalinformation. However, even words labeled “other” may be used to labelother tokens. For example, the phrase “by the” may be an importantindicator that what follows is the name of a musical artist,particularly when the words “by the” are preceded by a song title. Insome embodiments, the named entity recognizer 222 can use hints to aidprocessing. For example, hint information indicating that the inputlikely relates to the artist “Rolling Stones” can be used if the inputfrom the ASR does not match exactly the artist name “Rolling Stones,” orif “Rolling Stones” can apply to multiple named entities in the musicdomain 202 a (e.g., a song, album, and artist). In such cases, if thereare several different possible options for “Rolling Stones,” includingartist, the named entity recognizer can select or bias the resultstowards “Rolling Stones” being the artist.

The intent classifier 224 can receive input from the named entityrecognizer 222 and determine which intent, known to the single-domainNLU module 202, describes the most likely user intent. For example, thenamed entity recognizer 222 may label the token “play” as a user intent.The intent classifier 224 can determine which command or other responsemost likely captures the user intent. Illustratively, the music domainmay determine that a programmatic “playSong( . . . )” commandcorresponds best to the user intent. The command may include argumentsor parameters, such as one parameter for a song ID, or multipleparameters for the artist and song title. In some embodiments, theintent classifier 224 can use hints to aid processing. If an utterancecan apply to several different intents (e.g., play a song, buy a song,etc.), the hints can help the intent classifier 224 to select or biasthe results towards one that is consistent with the hint.

The cross domain ranker 204 can receive output from the severaldomain-specific NLU modules 202 a, 202 b and 202 c and combine theresults into a single result or N-best list of results. In someembodiments, domain-specific NLU modules 202 output an N-best list ofresults and scores associated with those results. The scores mayindicate a confidence in each result or a likelihood that each result isthe correct result. The cross domain ranker 204 can then combine each ofthe N-best lists into a single N-best list based on the scores.Returning to the example above, the music domain 202 a may produce anN-best list of interpretations and corresponding scores, and the scoresmay be between 0.70 and 0.99 (where 0 is the minimum score and 1 is themaximum score). The phone domain 202 c may also produce an N-best listof interpretations and corresponding scores. In the case of the phonedomain 202 c, however, the scores may be between 0.01 and 0.10. Each ofthe other domain-specific NLU modules 202 can produce its own N-bestlist of results and corresponding scores. The cross domain ranker 204can combine the scores into single sorted N-best list of results andcorresponding scores, such that the most likely interpretation is thefirst result in the N-best list or has the highest corresponding score.This scoring method is illustrative only, and not intended to belimiting. Other methods of scoring or ranking N-best lists, known tothose of skill in the art, may also or alternatively be used.

The technique described above can be used when domain-specific NLUmodules 202 are configured to recognize when an utterance is likelyoutside if its own domain. For example, the domain-specific NLU modules202 may be exposed to text from other domains during the trainingprocesses. Such domain-specific NLU modules 202 can assign lower scoresto their results—including the top result of the domain-specific N-bestlist—due to the reduced likelihood that the results are correct. Thecross domain ranker 204 can then simply combine the results into asingle N-best list or choose the best result, because thedomain-specific NLU modules 202 have already normalized the data basedon their ability to recognize when utterances are likely outside thespecific domain that they are configured to process.

In some embodiments, the domain-specific NLU modules 202 may not beconfigured to recognize when utterances are likely outside of theirspecific domains. In such cases, the cross domain ranker 204 cannormalize the scores from the domain-specific NLU modules 202 whengenerating the combined N-best list. Returning the previous example, themusic domain 202 a may return an N-best list of results with scoresbetween 0.70 and 0.99. The phone domain 202 c may also return an N-bestlist of results with scores between 0.70 and 0.99. The cross domainranker 204 can use hints to assign weights to the scores from thevarious domain-specific NLU modules 202 or to otherwise normalize theresults from the various domain-specific NLU modules 202. As a result,the cross domain ranker 204 can produce a combined N-best list that issorted according to normalized scores or which otherwise indicates whichresults are the most likely across results from all domain-specific NLUmodules 202.

The slot filler 206 can ensure that all data required to fully implementthe user intent is present, and can also remove any unnecessary data.For example, the domain-specific NLU modules 202 may use more data inproducing the N-best lists than is otherwise necessary for othercomponents of the spoken language processing system 100 to take actionin response to the user utterance. The slot filler 206 can thereforeremove unnecessary information from the NLU results or otherwise modifythe NLU results accordingly. In addition, the slot filler 206 can ensurethat all information necessary implement the user intent is present. Inthe present example, the user may have said “Give Me Shelter” whenissuing the voice command to play the song by the Rolling Stones. Theslot filler may determine that there is no song by the Rolling Stonescalled “Give Me Shelter.” By searching a catalog or other data store forsongs by the Rolling Stones with a similar name, the slot filler 206 maydetermine that correct interpretation is to play the song “GimmeShelter” by the Rolling Stones. In some cases, the slot filler 206 mayrequire more information from the user, and the dialog manager 116 maybe employed to prompt the user for the missing information. As anotherexample, the user utterance may be “Remind me to pay the bills on theday after tomorrow.” The user intent, as determined by the intentclassifier 224 in conjunction with the named entity recognizer 222, maycorrespond to execution of a command such as “createReminder( . . . ).”The command may require a parameter for the day on which the reminder isto be created. In addition, the command may require the day to bespecified unambiguously. The slot filler 206 can translate the phrase“day after tomorrow” into a specific date for use with the“createReminder( . . . )” command. For example, if the current data isNovember 9, then the slot filler 206 can calculate that the day to beused in the “createReminder( . . . )” command is November 11.

The context ranker 208 can use hints to select the most likely resultfrom the N-best list or to re-order the results in the N-best list. Forexample, the current hint may indicate that the user is likely issuing acommand to play a particular song. If the top-scored or most likelyresult in N-best list is that the user wants to buy the song “GimmeShelter” by the Rolling Stones, rather than play the song, the contextranker 208 can re-rank the results in the N-best list such that the mostlikely result is that the user wants to play the song. As describedabove, due to the multi-domain nature of the NLU module 114, users canissue voice commands related to any domain rather than only thepreviously used domain or a currently active domain. In some cases,therefore, the context ranker 208 may not necessarily select or elevatethe result that most closely corresponds to the current hint. Forexample, the most likely preliminary result in the N-best list may besubstantially more likely than the result that most closely correspondsto the current hint (e.g., the difference between scores associated withthe two items exceeds a threshold, or the result that most closelycorresponds to the current hint is ranked below a threshold). In suchcases, the context ranker 208 may not increase the score or rank of theresult that most closely corresponds to the hint.

Process for Managing Generation and Usage of Identifiers

With reference now to FIG. 4, a sample process 400 for managing thegeneration and usage of hints in a spoken language processing systemwill be described. Advantageously, a spoken language processing system100 may use the process 400 to save history data regarding userutterances and other interactions, and to generate hints based on prioruser utterances and interactions. The history and hints may be used inprocessing subsequent user utterances and interactions.

The process 400 begins at block 402. The process 400 may beginautomatically upon initiation of a speech recognition session. Theprocess 400 may be embodied in a set of executable program instructionsstored on a computer-readable medium, such as one or more disk drives,of a computing system of the spoken language processing system 100, suchas an orchestrator 110 server. When the process 400 is initiated, theexecutable program instructions can be loaded into memory, such as RAM,and executed by one or more processors of the computing system.

At block 404, the spoken language processing system 100 can receive anutterance from a client device 102. As described above, the userutterance may be a spoken command to play a recorded music file.

At block 406, the spoken language processing system 100 can accesshistory and/or hints that may be useful in processing the utterance. Asdescribed above, the history can be a record of user intents and/orresponses associated with the user within a particular time frame orduring a particular voice command session. Hints may be generated duringor after processing of user utterances and saved for use in processingsubsequent utterances. In some cases, data other than user utterancesmay be received from the client device 102. Such data may be saved inthe history and/or used to generate hints to aid in further processing,and those hints may be accessed at block 406 to process the currentutterance. For example, a user of a client device 102, such as a mobilephone, may raise the phone up to the user's head in a vertical position.The mobile phone may include proximity sensors to determine that thephone is currently positioned near the user's head. Data regarding thisparticular user action may be transmitted to the spoken languageprocessing system 100 and stored as history. Such a user action mayindicate that he user is about to initiate voice dialing, and thereforethe data may be useful in generating hints, as described below.

At block 408, the spoken language processing system 100 can process theutterance as described in detail below with respect to FIG. 5. At block410, history and hints based on the utterance, the processing of theutterance, and/or the response generated may be saved for use inprocessing further utterances.

Subsequent to, or in parallel with, saving history and/or hints, theorchestrator 110 can determine at decision block 412 whether a responseis to be sent to the client device 102. For example, if an utterance isreceived that includes a request for playback of a particular musicalrecording, such as Beethoven's 5th Symphony, the dialog manager 116 ofthe spoken language processing system 100 may prompt the user toidentify the particular recording artist (e.g., the Chicago SymphonyOrchestra or the Berlin Symphony Orchestra). As described in detailherein, a TTS audio response prompting the user for the name of therecording artist may be generated and ready for transmission to theclient device 102. In addition, history may be saved regarding theprompt, and the history can be used during a subsequent execution of theprocess 400. If a prompt, executable command, or some other response isready for transmission, the orchestrator 110 can transmit the responseto the client device 102 at block 414. Otherwise, the process 400 canterminate.

Data received subsequent to the execution of the process 400 may causethe process 400 to be executed again. Returning to an example describedabove, the user may provide a response to a prompt for a particularrecording artist by submitting the utterance “the Chicago SymphonyOrchestra.” At block 406, data regarding the history and/or hints savedduring previous executions of the process 400 may be accessed, and atblock 408 the utterance may be processed. Based on the history (e.g., arequest for playback of a Beethoven's 5th Symphony followed by a promptfor an artist's name), the hint used during processing of thesubsequently received utterance may indicate that the utterance likelyrelates to an artist for the request to play a musical recording ofBeethoven's 5th symphony.

Multi-Domain NLU Processing of a User Utterance

FIG. 5 illustrates a sample process 500 for processing a user utterance,received from a client device 102, with a multi-domain NLU engine.Advantageously, the process 500 may be used to process user utterancesin multiple domains simultaneously or substantially simultaneously, andto select the best result or result most likely to be accurate fromamong the multiple results that are calculated.

The process 500 begins at block 502. The process 500 may beginautomatically upon receipt of an utterance from a client device 102. Theprocess 500 may be embodied in a set of executable program instructionsstored on a computer-readable medium, such as one or more disk drives,of a computing device associated with the spoken language processingsystem 100. When the process 500 is initiated, the executable programinstructions can be loaded into memory, such as RAM, and executed by oneor more processors of the computing system.

At block 504, an utterance may be received by the spoken languageprocessing server 100. For example, the user may have submitted a spokencommand to initiate playback of a particular music recording. (e.g.,“play Beethoven's 5th symphony by the Chicago Symphony Orchestra”). Atblock 506, the utterance may be transcribed into a likely transcriptionor N-best list of likely transcriptions by an ASR module 112 of thespoken language processing system 100. If any hints are available, theymay be provided to the ASR module 112 in order to allow ASR module 112to operate more efficiently and provide potentially more accurateresults.

At blocks 508-1 to 508-n, the transcription or N-best list of likelytranscriptions may be processed by any number of single-domain NLUmodules in a multi-domain NLU engine. Each domain may process thetranscription with respect to a particular subject matter, as describedabove. The domains may process the transcription in parallel orasynchronously so as to reduce the user-perceived time required toperform multi-domain NLU processing in comparison with single-domain NLUprocessing. In addition, a score may be assigned to each of the results.

At block 510, the most likely interpretation of user intent may beselected from the N-best list returned from the various single domainNLU modules. In some embodiments, response is selected based on the hintthat was generated during or after processing of a previously receivedutterance or after receiving other information from the client device102.

At block 512, the spoken language processing system 100 may determine aresponse to the utterance. The response can vary depending upon whichdomain provided the most likely analysis of the user's intent. Returningto the previous example, if the music domain produced an analysis of theutterance with the highest score, then an executable command to play therequested music may be the most appropriate response. However, if notall of the required information was included in the utterance, a promptmay be generated in order to get the additional information.

At decision block 514, the spoken language processing system candetermine whether the response includes content to be presented aurallyto the user, such a text that is to be read to the user. For example, ifthe spoken language processing system 100 determined that the user is tobe prompted for additional information regarding the user's utterance,then the process may proceed to block 516. Otherwise, if no TTSprocessing is required, the process 500 may proceed to block 520, wherea command corresponding to the likely user intent is generated or someother action is performed.

At block 516, an NLG module 118 may be employed to generate text for aspoken response such that the language of the response will soundnatural to the user. For example, if the user has requested informationabout a particular product, information about the product (e.g., price,features, availability) may be obtained and provided to the NLG module118. The NLG module 118 may output a string of text that can besynthesized as speech by a TTS module 112. At block 518, the TTS module112 can generate synthesized speech from a text input, such as textgenerated by an NLG module 118.

Depending on the embodiment, certain acts, events, or functions of anyof the processes or algorithms described herein can be performed in adifferent sequence, can be added, merged, or left out altogether (e.g.,not all described operations or events are necessary for the practice ofthe algorithm). Moreover, in certain embodiments, operations or eventscan be performed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors or processor cores or onother parallel architectures, rather than sequentially.

The various illustrative logical blocks, modules, routines and algorithmsteps described in connection with the embodiments disclosed herein canbe implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modulesand steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. The described functionality can beimplemented in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the disclosure.

The steps of a method, process, routine, or algorithm described inconnection with the embodiments disclosed herein can be embodieddirectly in hardware, in a software module executed by a processor, orin a combination of the two. A software module can reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of a non-transitorycomputer-readable storage medium. An exemplary storage medium can becoupled to the processor such that the processor can read informationfrom, and write information to, the storage medium. In the alternative,the storage medium can be integral to the processor. The processor andthe storage medium can reside in an ASIC. The ASIC can reside in a userterminal. In the alternative, the processor and the storage medium canreside as discrete components in a user terminal.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orsteps. Thus, such conditional language is not generally intended toimply that features, elements and/or steps are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or steps are included or are to beperformed in any particular embodiment. The terms “comprising,”“including,” “having,” and the like are synonymous and are usedinclusively, in an open-ended fashion, and do not exclude additionalelements, features, acts, operations and so forth. Also, the term “or”is used in its inclusive sense (and not in its exclusive sense) so thatwhen used, for example, to connect a list of elements, the term “or”means one, some, or all of the elements in the list.

Conjunctive language such as the phrase “at least one of X, Y and Z,”unless specifically stated otherwise, is to be understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y or Z, or a combination thereof. Thus, such conjunctivelanguage is not generally intended to imply that certain embodimentsrequire at least one of X, at least one of Y and at least one of Z toeach be present.

While the above detailed description has shown, described and pointedout novel features as applied to various embodiments, it can beunderstood that various omissions, substitutions and changes in the formand details of the devices or algorithms illustrated can be made withoutdeparting from the spirit of the disclosure. As can be recognized,certain embodiments of the inventions described herein can be embodiedwithin a form that does not provide all of the features and benefits setforth herein, as some features can be used or practiced separately fromothers. The scope of certain inventions disclosed herein is indicated bythe appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A system comprising: a computer-readable memorystoring executable instructions; and one or more processors incommunication with the computer-readable memory, wherein the one or moreprocessors are programmed by the executable instructions to at least:receive text corresponding to a request of a user; process the text in afirst natural language understanding (“NLU”) module to generate a firstinterpretation of the text, and in a second NLU module to generate asecond interpretation of the text, wherein the first NLU module isassociated with a first domain, and the second NLU module is associatedwith a second domain, wherein the first interpretation is associatedwith a first score indicative of a confidence in the firstinterpretation, and wherein the second interpretation is associated witha second score indicative of a confidence in the second interpretation;select the first interpretation based at least partly on the first scoreand the second score; and generate a response based at least partly onthe first interpretation.
 2. The system of claim 1, wherein theexecutable instructions that program the one or more processors toprocess the text in the first NLU module comprise executableinstructions to: separate at least a portion of the text into aplurality of tokens, wherein the text comprises a plurality of words,and wherein individual tokens of the plurality of tokens comprise one ormore words of the of the plurality of words; identify at least a firsttoken of the plurality of tokens as corresponding to an executablecommand; and identify at least a second token of the plurality of tokensas a parameter of the executable command.
 3. The system of claim 1,wherein the first interpretation comprises a plurality of namedentities, wherein individual named entities of the plurality of namedentities correspond to one or more tokens of the text, and wherein atleast one of the plurality of named entities corresponds to anexecutable command.
 4. The system of claim 1, wherein the first NLUmodule is configured to generate interpretations of text as comprisingrequests related to the first domain, and wherein the first domaincomprises requests related to phone dialing, shopping, gettingdirections, playing music, or performing a search.
 5. The system ofclaim 1, wherein the confidence in the first interpretation comprises alikelihood that the first interpretation is correct.
 6. The system ofclaim 1, wherein the confidence in the first interpretation is based onwhether an executable command corresponds to the first interpretation.7. The system of claim 1, wherein the executable instructions furtherprogram the one or more processors to rank the first interpretation andthe second interpretation using the first score and the second score,wherein the first interpretation is ranked higher than the secondinterpretation, and wherein selecting the first interpretation comprisesselecting a highest-ranked interpretation of the text.
 8. The system ofclaim 1, wherein the executable instructions further program the one ormore processors to at least: store hint information regarding theresponse, wherein the response comprises a prompt for additionalinformation regarding the request, and wherein the hint informationindicates that a subsequent text will likely relate to the additionalinformation; receive the subsequent text in response to the prompt;process the subsequent text in the first NLU module to generate a thirdinterpretation of the subsequent text, and in the second NLU modulegenerate a fourth interpretation of the subsequent text, wherein thethird interpretation is associated with a third score indicative of aconfidence in the third interpretation, and wherein the fourthinterpretation is associated with a fourth score indicative of aconfidence in the fourth interpretation; determine that the thirdinterpretation corresponds to the additional information indicated bythe hint information; and increase the third score.
 9. Acomputer-implemented method comprising: under control of one or morecomputing devices configured with specific computer-executableinstructions, receiving text corresponding to a request of a user;processing the text in a first natural language understanding (“NLU”)module to generate a first interpretation of the text, and in a secondNLU module to generate a second interpretation of the text, wherein thefirst NLU module is associated with a first domain, and the second NLUmodule is associated with a second domain, wherein the firstinterpretation is associated with a first score indicative of aconfidence in the first interpretation, and wherein the secondinterpretation is associated with a second score indicative of aconfidence in the second interpretation; selecting the firstinterpretation based at least partly on the first score and the secondscore; and generating a response based at least partly on the firstinterpretation.
 10. The computer-implemented method of claim 9, whereinprocessing the text in the first NLU module to generate the firstinterpretation comprises: separating at least a portion of the text intoa plurality of tokens, wherein the text comprises a plurality of words,and wherein individual tokens of the plurality of tokens comprise one ormore words of the of the plurality of words; identifying at least afirst token of the plurality of tokens as corresponding to an executablecommand; and identifying at least a second token of the plurality oftokens as a parameter of the executable command.
 11. Thecomputer-implemented method of claim 9, wherein the first interpretationcomprises a plurality of named entities, wherein individual namedentities of the plurality of named entities correspond to one or moretokens of the text, and wherein at least one of the plurality of namedentities corresponds to an executable command.
 12. Thecomputer-implemented method of claim 9, wherein the first NLU module isconfigured to generate interpretations of text as comprising requestsrelated to the first domain, and wherein the first domain comprisesrequests related to phone dialing, shopping, getting directions, playingmusic, or performing a search.
 13. The computer-implemented method ofclaim 9, wherein the confidence in the first interpretation comprises alikelihood that the first interpretation is correct.
 14. Thecomputer-implemented method of claim 9, wherein the confidence in thefirst interpretation is based on whether an executable commandcorresponds to the first interpretation.
 15. The computer-implementedmethod of claim 9, further comprising ranking the first interpretationand the second interpretation based at least partly the first score andthe second score, wherein the first interpretation is ranked higher thanthe second interpretation, and wherein selecting the firstinterpretation comprises selecting a highest-ranked interpretation ofthe text.
 16. The computer-implemented method of claim 9, furthercomprising: storing hint information regarding the response, wherein theresponse comprises a prompt for additional information regarding therequest, and wherein the hint information indicates that a subsequenttext will likely relate to the additional information; receiving thesubsequent text in response to the prompt; processing the subsequenttext in the first NLU module to generate a third interpretation of thesubsequent text, and in the second NLU module generate a fourthinterpretation of the subsequent text, wherein the third interpretationis associated with a third score indicative of a confidence in the thirdinterpretation, and wherein the fourth interpretation is associated witha fourth score indicative of a confidence in the fourth interpretation;determining that the third interpretation corresponds to the additionalinformation indicated by the hint information; and increasing the thirdscore.
 17. Non-transitory computer readable storage storing executablecode that, when executed, causes one or more computing devices toperform a process comprising: receiving text corresponding to a requestof a user; processing the text in a first natural language understanding(“NLU”) module to generate a first interpretation of the text, and in asecond NLU module to generate a second interpretation of the text,wherein the first NLU module is associated with a first domain, and thesecond NLU module is associated with a second domain, wherein the firstinterpretation is associated with a first score indicative of aconfidence in the first interpretation, and wherein the secondinterpretation is associated with a second score indicative of aconfidence in the second interpretation; selecting the firstinterpretation based at least partly on the first score and the secondscore; and generating a response based at least partly on the firstinterpretation.
 18. The non-transitory computer readable storage ofclaim 17, wherein the first interpretation comprises a plurality ofnamed entities, wherein individual named entities of the plurality ofnamed entities correspond to one or more tokens of the text, and whereinat least one of the plurality of named entities corresponds to anexecutable command.
 19. The non-transitory computer readable storage ofclaim 17, wherein the confidence in the first interpretation comprises alikelihood that the first interpretation is correct.
 20. Thenon-transitory computer readable storage of claim 17, wherein theconfidence in the first interpretation is based on whether an executablecommand corresponds to the first interpretation.